linux-kernel - RE: [PATCH] cxl/mbox: Fix debug message print

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Date:   Tue, 1 Aug 2023 11:45:05 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Alison Schofield" <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>
CC:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Ira Weiny <ira.weiny@...el.com>
Subject: RE: [PATCH] cxl/mbox: Fix debug message print

Dan Williams wrote:
> Ira Weiny wrote:
> > The handle value used to report an event being cleared by dev_dbg() is
> > incorrect due to a post increment of the payload handle index.
> > 
> > Delay the increment of the index until after the print.  Also add the
> > debugging for event processing which was useful in finding this bug.
> > 
> > To: Davidlohr Bueso <dave@...olabs.net>
> > To: Jonathan Cameron <jonathan.cameron@...wei.com>
> > To: Dave Jiang <dave.jiang@...el.com>
> > To: Alison Schofield <alison.schofield@...el.com>
> > To: Vishal Verma <vishal.l.verma@...el.com>
> > To: Dan Williams <dan.j.williams@...el.com>
> 
> Is this some new process recommendation to use "To:", I would only
> expect Cc: for maintainers.

It is just what b4 does because all those folks are listed as maintainers.

> 
> > Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> 
> Jonathan gets listed twice because?

That is odd.  I did not notice that.

> 
> > Cc: linux-cxl@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> 
> I assume this is because b4 takes its address from the patch itself?
> 
> It just feels a bit too noisy.

Yea b4 generated the list and I just copied it here.  Vishal is correct
that this is automatically put in the tracking cover letter commit b4 uses
but I copied it here because it was not a series.  I'll skip this in the
future.

> 
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > ---
> > NOTE: This does fix a bug in the patch referenced below.  However, I
> > don't think that warrants back porting because this is only a debug
> > print.
> 
> I don't think that's a reason not to flag for backport. Smaller things
> than this have been backported, and if it saves someone getting confused
> in the field its worth it.

Ok.

> 
> > 
> > Fixes: 6ebe28f9ec72 ("cxl/mem: Read, trace, and clear events on driver load")
> > ---
> >  drivers/cxl/core/mbox.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> > index d6d067fbee97..f052d5f174ee 100644
> > --- a/drivers/cxl/core/mbox.c
> > +++ b/drivers/cxl/core/mbox.c
> > @@ -882,9 +882,10 @@ static int cxl_clear_event_record(struct cxl_memdev_state *mds,
> >  	 */
> >  	i = 0;
> >  	for (cnt = 0; cnt < total; cnt++) {
> > -		payload->handles[i++] = get_pl->records[cnt].hdr.handle;
> > +		payload->handles[i] = get_pl->records[cnt].hdr.handle;
> >  		dev_dbg(mds->cxlds.dev, "Event log '%d': Clearing %u\n", log,
> >  			le16_to_cpu(payload->handles[i]));
> > +		i++;
> >  
> >  		if (i == max_handles) {
> >  			payload->nr_recs = i;
> > @@ -946,9 +947,13 @@ static void cxl_mem_get_records_log(struct cxl_memdev_state *mds,
> >  		if (!nr_rec)
> >  			break;
> >  
> > -		for (i = 0; i < nr_rec; i++)
> > +		for (i = 0; i < nr_rec; i++) {
> > +			dev_dbg(dev, "Event log %d: processing handle %u\n",
> > +				type,
> > +				le16_to_cpu(payload->records[i].hdr.handle));
> >  			cxl_event_trace_record(cxlmd, type,
> >  					       &payload->records[i]);
> 
> This looks unrelated to the fix.

It helped me to debug the issue.  Since you want this marked as a fix for
backport I will split this out.  Potentially just squash it into some
other patch or make it stand alone.

Ira